Field of the Invention
The present invention relates generally to systems, devices, and methods for observing, testing, and/or analyzing one or more biological samples, and more specifically to systems, devices, and methods comprising an optical system for observing, testing, and/or analyzing one or more biological samples.
Description of the Related Art
Optical systems for biological and biochemical reactions have been used to monitor, measure, and/or analyze such reactions in real time. Such systems are commonly used in sequencing, genotyping, polymerase chain reaction (PCR), and other biochemical reactions to monitor the progress and provide quantitative data. For example, an optical excitation beam may be used in real-time PCR (qPCR) reactions to illuminate hybridization probes or molecular beacons to provide fluorescent signals indicative of the amount of a target gene or other nucleotide sequence. Increasing demands to provide greater numbers of reactions per test or experiment have resulted in instruments that are able to conduct ever higher numbers of reactions simultaneously.
The increase in the number sample sites in a test or experiment has led to microtiter plates and other sample formats that provide ever smaller sample volumes. In addition, techniques such as digital PCR (dPCR) have increased the demand for smaller sample volumes that contain either zero or one target nucleotide sequence in all or the majority of a large number of test samples. The combination of small feature size (e.g., an individual sample site or volume) and large field of view to accommodate a large number of test samples has created a need for optical systems that provide high optical performance with relatively small sample signals.
The reduction in sample volumes has also lead to a desire to incorporate light sources that provide a large amount output power or intensity. In recent years, advance in LED (Light Emitting Diode) technology resulted in availability of LED sources with significantly larger outputs. In addition, high power LED sources are now available with a broad spectrum, for example, white light LEDs that provide significant output power across the visible spectrum. Broad spectrum or white light LEDs are also attractive in biological applications such as PCR, since they allow for a broad range of dyes or markers to be used in a single sample or instrument. However, high power LEDs can have large power and spectral variations from the nominal specification. Thus, various LEDs having the same part number or output specification may result in unacceptably large instrument to instrument variation, particularly would couple with other system tolerance variation (e.g., variations in filter and beamsplitter optical characteristics). Thus, there exists a need for better control and calibration systems, devices, and methods when attempting to incorporate high power, broad spectrum LED into biological instruments.